Devices of the aforesaid type are widely used in packaging lines for confectionary products, such as chocolate bars, biscuits or others of similar type, in which such products are moved, on conveying lines, disposed in ranks or groups of ranks spaced from one another (by ranks there are meant in the present context rows of aligned products, in which the rows are disposed perpendicularly to the direction of advance of the products). Between these conveying lines and the packaging machines there is typically interposed a storage unit for the products to permit regular feeding at a predetermined and uniform rhythm of the packaging machine, and thus to render said feeding independent of the speed and variations in the flow of the incoming ranks.
With such storage units it is therefore possible to feed efficiently different automatic packaging lines having speeds and feeding rhythms programmed according to the type of product being dealt with.
Typically, such storage units comprise a magazine within which a plurality of container elements is supported and conducted in series along a path which optimizes the storage capacity. In general, the containers are regularly spaced from one another at a predetermined pitch and each comprises a plurality of shelves capable of supporting and containing respective ranks of products. The provision of one or more conveyor chains on which the containers are secured at a regular pitch is typical.
The slide path of the chain is further selected such that each container is conducted in sequence to the receiving opening for loading onto each of its shelves one or more ranks of products coming into the storage unit and, at the same time, a previously loaded container is conducted, by the effect of movement of the chain, to the delivery opening for the release of the products leaving the storage unit.
Storage units of this type normally extend in height and provide a vertical ascending section of the chain for loading the containers in sequence through the receiving opening and a descending vertical section of the chain for positioning the containers at the delivery opening and consequently unloading the products from the storage unit. These sections are part of the overall path, which may furthermore have a certain number of bends or returns having the function of maximizing the number of containers (and therefore of products) that can be accumulated within the storage unit.
A limit to be encountered in the known storage devices having the aforesaid characteristics lies in the fact that the distance between the last support shelf of one container and the first shelf of the container following it is generally different from the pitch existing between adjacent shelves of the same container. This makes it necessary to move the chain at different speeds in order to guarantee the same loading rhythm when passing from the last shelf of one container to the first shelf of the following container, both in the loading phase and in the phase of unloading of the products from the storage unit. This inequality of pitches produces accelerations and decelerations of the containers which may induce disturbing dynamic stresses in the movement of the containers themselves, for example inducing unwanted oscillating movements.
To these dynamic actions are further added unwanted swaying movements of the containers induced when passing through the winding sections of the path, which sections are produced by the bends of the chain created within the magazine to increase the storage capacity thereof. The rotational and translational movements induced by such curved paths may further compromise the alignment of the ranks of products supported in the containers. On the other hand, a limitation of such stresses and swaying movements is obtainable by reducing the speed of translation of the chain, thus requiring, however, much greater storage times for the loading of the magazine, to the detriment of the overall efficiency and productivity of the plant.